This invention relates broadly to solid propellant rocket motors. Particularly, it relates to methods and apparatus for eliminating stresses ordinarily caused by differential expansion or contraction of the propellant grain and the case to which it is bonded.
A continuing problem with solid propellant rocket motors, particularly those of the end burning type, is that most solid propellants tend to shrink to a much greater degree than the rocket motor case to which they are customarily bonded, during their curing process and also when subjected to lowered ambient temperatures.
Conventional methods of obviating these stresses have included the use of a plurality of layers of insulaton surrounding the propellant grain. These layers are bonded together and to the case of the rocket only at the forward end thereof to permit longitudinal movement of the propellant grain relative to the case as it shrinks or expands. This method tended to add an unacceptable amount of inert weight to the rocket and to diminish the quantity of propellant that could be loaded into the case.
The present invention provides a solution to this problem by a means that is both lighter in weight and easier to manufacture.